The invention involves a sensor having a temperature-dependent measuring resistance (resistor), that is connected by a connection contact to an evaluation circuit and is flowed through by an impressed current, wherein a voltage signal dropping across the measuring resistor is determined, which relates to its temperature in an at least approximately linear proportional manner, wherein the measuring resistor is electrically connected at one end both with a constant current source as well as with an electrical circuit in order to output a temperature-voltage signal, while a connection point of a series connection made of the measuring resistor and a reference resistance is connected to the electrical circuit. The invention also relates to a use of the sensor in an electrical circuit for temperature measurement.
From U.S. Pat. No. 3,613,454 a device is known for temperature measurement using a temperature-sensitive measuring resistor that is flowed through by an impressed current, wherein the voltage generated on the measuring resistor is supplied as an input signal to a differential amplifier, whose output forms a voltage output signal that is at least approximately linearly proportional to the measuring resistor temperature. For this purpose, the impressed current is supplied from the output of a first differential amplifier to the measuring resistor connected to the input of a second differential amplifier, such that the current flows through a reference resistor that is connected to it in series, whose voltage is supplied as a signal for inverse feedback to the input of the first differential amplifier for the purpose of stabilizing the impressed current.
It proves to be problematic that the construction of temperature sensors using wound platinum wire is relatively expensive.
Furthermore, from published German patent application DE 24 60 648 A1, a circuit arrangement is known for measuring temperature using a platinum resistance thermometer in linear relation to the output voltage, wherein as a function of a reference voltage, a differential amplifier impresses onto the platinum resistance, acting as a temperature sensor, a current that remains constant with the value of the platinum resistance, so that the voltage on the platinum resistance increases linearly with the temperature. In this way, using a suitably dimensioned differential amplifier, a voltage is generated against the reference voltage in such a way that the voltage offset for the initial temperature of a given temperature range disappears. For larger currents through the platinum resistance, the intrinsic heating can be reduced by an impulse sequence with the amplitude of the input voltage.
For temperature equalization of ovens, the desired temperature level of a temperature regulator is linearly preset as a voltage value. The desired voltage value can be obtained from the reference voltage using a potentiometer circuit; furthermore, the desired voltage value can also be preset by a digital-analog converter. This involves a relatively expensive arrangement for operating several ovens, wherein the respective components such as the comparator, digital memory, platinum thermometer, digital-analog converter, and progress control form their own respective circuit arrangements.
Furthermore, from published German patent application DT 22 08 852, a circuit arrangement is known for generating a linear temperature-dependent electric quantity using a resistor bridge circuit, wherein one of the bridge resistors is constructed as a platinum measuring resistor; the bridge diagonal being formed by a differential amplifier. In particular, the linearity of the platinum sensor is obtained by an inverse feedback effect that exceeds the positive feedback; the positive feedback thereby linearizes the output signal in reference to the temperature characteristic, whereby the inverse feedback prevents a tendency to oscillate.
This thus involves a circuit arrangement having many electronic components that is technically and spatially relatively expensive.